The invention relates to an operating method and system for supporting lane keeping of a vehicle according to the independent claims.
Unintentional lane departure, i.e. leaving the lane or at least a desired position in the lane, is a relevant cause of road accidents involving all sorts of vehicles, including heavy duty, medium duty or light duty vehicles. Besides technical problems, known reasons for such lane departures are driver distraction, inattention or drowsiness. It is known in the art to provide support means for a driver to avoid unintentional lane departure of the vehicle.
US 2006/047390 A1 discloses to use an adaptive torque which will increase or decrease dependent on the lateral deviation of the vehicle from a desired position. A torque can be transmitted to the steering wheel either directly when the vehicle is deviating from the lane centre or when the vehicle is close to a borderline of the road.
US 2006/217860 A1 discloses a lane keeping assistant apparatus which assists a steering force when the vehicle is about to deviate from the lane to provide the driver with improved steering feeling. A position of a vehicle, lane centre locating means, calculation means for calculating a lateral deviation from a desired position relative to the centre and a power source for providing an assist torque are used by an assist torque determining means for determining the assist torque to be provided by the power source. The assist torque determining means gradually reduces the assist torque if the lateral deviation amount is being reduced by a driver's steering operation.
In a paper of M. Montiglio et al., entitled “Development of a lane keeping support system for heavy trucks” published in www.prevent-ip.org/download/Events/20061008-12_ITS_WC_London/TS128/Paper%202180.pdf, a haptic lane keeping support system is described which provides an additional resistant torque to the steering wheel which is opposite to the torque exerted by the driver onto the steering wheel in order to alert the driver that the vehicle is unintentionally about to move out of its lane. During a borderline approaching/crossing and with deactivated direction indicators the system evaluates this event as unintentional and applies an additional resistant torque to the steering wheel to oppose the lane departure.
It is desirable to provide an operating method and system for lane keeping of a vehicle which supports the driver while the driver has still full authority to steer the vehicle.
An operating method according to an aspect of the present invention is proposed for supporting lane keeping of a vehicle, equipped with a steering device for steering the vehicle. The method comprises the steps of providing vehicle related information, providing environment related information, combining vehicle and environment related information, predicting a future trajectory of the vehicle based on vehicle and environment related information, estimating a desired lane position of the vehicle and/or a guiding force, comparing the future trajectory and the desired lane position, deciding if a guiding force is to be provided to the steering device, and, if guiding force is to be provided, defining an amount of said guiding force depending on a hierarchically ordered set describing a predetermined driving behavior of the vehicle, adapting said amount of guiding force depending on the direction in which the vehicle is intended to move and activating one or more actuators for supplying said adapted amount of guiding force to said steering device.
The method is applicable for all kind of vehicles and is in particular suitable for heavy duty, medium duty and light duty vehicles.
One important aspect of the method is that it helps decreasing the risk of unintended departure of the vehicle from a desired lateral position on a road or in a lane of a road, i.e. leaving the lane or the road or a desired position in the lane or on the road
The guiding force is exerted onto the steering device which is resistive if counteracting the force applied by the driver onto the steeling device, or supportive if acting in the same direction as the force applied by the driver onto the steering device, thus for instance reducing the effect of e.g. frictional forces acting on the wheels and the like which are experienced by the driver as resistance when operating the steering device. The steering device can be for instance a conventional steering wheel, a joystick, a sliding nipple or any other steering device suitable for steering the vehicle. For instance, in case that the steering device is a steering wheel the guiding force will appear as a guiding torque exerted onto the steering wheel.
Another aspect of the method according to the invention is that the lane keeping support system will provide such—additional—guiding force only in situations in which the supply of such guiding force to the steering device is deemed by the system to be appropriate after the analysis of all input data received by the system.
The driver experiences said guiding force (if applied) as an increasing or increased resistance of the steering device (for instance a steering wheel or joy stick) when operating the steering device in the “wrong”, i.e. non-desired way, for instance turning the steering wheel in the “wrong” direction moving the vehicle away from the desired lateral position on the road or in the lane of the road. Compared to that increasing or increased resistance the driver experiences-a decreasing or decreased resistance of the steering device when operating the steering device in the “right”, i.e. desired way, for instance turning the steering wheel in the “right” direction moving the vehicle towards the desired lateral position on the road or in the lane of the road.
However, the guiding force can never by itself move the steering wheel as that force can only increase or decrease resistance which the driver experiences when operating the steering device, for instance when turning the steering wheel of the vehicle.
According to a first preferred mode of operation of the lane keeping support system, the guiding force can be either “positive” or “negative” or zero when added to the normal force exerted by the driver and, if applicable, a conventional servo steering system, onto the steering device thus increasing the total resistance experienced by the driver when the steering device is moved in the “wrong” direction and decreasing the total resistance when the steering device is moved in the “right” direction. Preferably, the amount of guiding force can be varied in accordance with operation conditions and/or an actual state of the vehicle. “State of the vehicle” is a summary of relevant properties of the vehicle, such as e.g. lateral position in the lane, lateral velocity, and can also comprise additional geometrical parameters such as e.g. width, length, height, weight of towing vehicle and/or trailer (if attached).
More specifically, the guiding force is deemed to have a positive value if it counteracts the force exerted by the driver and, if applicable, a servo steering system, onto the steering device, i.e. if it acts in the opposite direction of the force exerted by the driver and, if applicable, the servo steering system. Such a positive force is experienced by the driver as an increasing or increased resistance of the steering device when operating the steering device, e.g. turning the steering wheel if the steering device is a steering wheel by way of example.
The guiding force is deemed to have a negative value if it acts in the same direction as the force exerted by the driver and, if applicable, a servo steering system onto the steering device. Such a negative force is experienced by the driver as a decreasing or decreased resistance of the steering device when operating the steering device. The overall effect of a negative guiding force is supporting the driver in operating the steering device and in this respect the supportive effect of such negative guiding force is comparable with the supportive effect the driver experiences due to the force exerted by a conventional servo system onto the steering device. Such a negative force can, for instance, support a servo system by further removing a residual resistance of the steering device.
Zero value means that there is no additional guiding force exerted onto the steering device.
According to second preferred mode of operation of the lane keeping support system, the guiding force can be applied in such a way as to always be positive, i.e. as to always counteract the actions of the driver when moving the steering device in the “wrong” direction and/or in an inappropriate way, thereby increasing the resulting total resistance which the driver experiences when operating the steering device. Preferably, the amount of guiding force can be varied with operation conditions and/or an actual state of the vehicle.
According to a third preferred mode of operation of the lane keeping support system, the guiding force can be applied only in cases when the steering device is moved in the “wrong” direction without adaptation of the amount of force to operating conditions and/or an actual state of the vehicle. When turning the steering device in the “right” direction, a conventional servo steering system can support the driver in the usual (and generally known) way.
Further, the guiding force can be applied to the steering device as a continuous force-function or, alternatively, can be triggered only in situations when the current lateral position of the vehicle deviates from a desired lateral position and/or the vehicle's current state deviates from a desired state of the vehicle.
Advantageously, as described above, a force-function can be provided describing the variation, i.e. the increase and for decrease of the guiding force. The force-function can depend on at least one of the lateral distance from the desired lateral position, the lateral velocity of the vehicle, the lateral acceleration of the vehicle, and the curvature of the lane. The force-function can be a continuous function and e.g. be linearly dependent or can depend in a non-linear form, e.g. be a quadratic dependency, an exponential dependency or the like on at least one of lateral distance, lateral velocity, lateral acceleration of the vehicle and curvature of the lane. The actual force-function is preferably chosen in a way which ensures the driving stability of the vehicle and/or is comfortable for the driver. It is possible to provide different force-functions for different situations, e.g. for travelling a curved trajectory along a bend or for travelling on straight roads. Designing or defining the one or more force-functions can be done by using at least one of the group of an expert system, an artificial intelligence, and fuzzy logic system, considering the hierarchically ordered set describing the desired driving behavior of the vehicle.
Since the lane keeping support system is supposed to encourage the driver to keep the vehicle in the desired lateral position on the road or in the lane of the road, or to move the vehicle towards said desired lateral position, the driver experiences an increasing resistance when he operates the steering device, for instance turns the steering wheel, such that the vehicle is driving in a direction opposite to the desired, i.e. “right”, direction towards the desired lateral position or the road or in the lane of the road.
Preferably, the hierarchically ordered set describing the predetermined driving behavior is a set of instructions. Preferably the set is prioritized in the order of                (i) stabilizing the vehicle;        (ii) preventing the vehicle from leaving the lane;        (iii) supporting the turning of the vehicle when driving a curved trajectory on a road, i.e. when the vehicle is driving on a road with a bend in the road wherein the bend is curved and vehicles travelling around or along the bend follow a curved trajectory.        
By prioritizing the predetermined driving behavior in this order a driving safety can be achieved in a reasonable way. If the vehicle is not in the desired lateral position or is leaving the desired lateral position, e.g. the centre of the lane of the road, the lateral velocity of the vehicle can be decreased or limited thus stabilizing the vehicle. “Lateral velocity” is to be understood as a velocity lateral to the regular driving direction of the vehicle.
Stabilizing the vehicle in the first instance allows the driver to react to a probably critical situation with the vehicle under full control. Thus, the vehicle can react properly to steering movements of the driver. Even if the vehicle should leave the lane, with a stabilized vehicle a greater level of security is achieved compared to a vehicle which is in an unstable condition. If supporting measures which prevent the vehicle from leaving the lane (with a stabilized vehicle) is prioritized over supporting the turning of the vehicle, the probability that critical situations caused by lane departure will occur can be minimized.
Advantageously, at least one of a lateral displacement, a lateral velocity, a lateral acceleration of the vehicle and a curvature of the road can be used as reliable input variables of vehicle related parameters for selecting the predetermined driving behavior out of the set describing the predetermined driving behavior.
The predetermined driving behavior can be determined by at least one of an expert system, an artificial intelligence system, and a fuzzy logic system. Advantageously, determining the amount of guiding force can be done by at least one of an expert system, an artificial intelligence system, and a fuzzy logic system. Using fuzzy logic, for instance, allows for obtaining a mathematical description of rules which can be used in a computer system although the rules themselves are not verbalized in a mathematical form but in a linguistic form. Favorably, by way of fuzzy a logic system can be controlled in a reasonable manner even if a mathematical relationship between input and output parameters of the system is very complex or cannot even be established. The actual specific value of the guiding force can preferably be set by a fuzzy logic function and is based on at least one of lateral position of the vehicle, lateral velocity of the vehicle, lateral acceleration of the vehicle, and lane curvature.
By using an expert system a selection of the appropriate predetermined driving behavior can be done based on expert knowledge bases. In an expert system the knowledge base is the field of the system which contains expert knowledge in an arbitrary representation form. The knowledge base is supplemented by an inference machine, i.e. a hardware or software which can operate on the basis of the knowledge base. Typical tasks for an expert system can be data interpretation, i.e. analysis of data, particularly understanding the data; survey, i.e. interpretation of data for initiating actions depending on an incidence; prognosis, i.e. anticipating and validating of accessible states of time variant systems.
By using artificial intelligence systems intelligent behavior can be analyzed and used for conclusions for future operations. Repeated operations or informations can be stored as empirical values which are the basis for recognizing regularities. Thus, general rules can be deducted from a multitude of data. An expert system could be understood as a part of an artificial intelligence system.
It is to be understood that each system can be used exclusively. However, a combination of two or more of the systems is also possible.
Preferably, at least the environment related data can be treated with data fusion. Favorably, data fusion allows combining data from multiple^ sources and gathering respective information in order to achieve inferences, which is more efficient than being achieved by means of a single source. Appropriate sensors for collecting the environment related data can be e.g. long range radar to detect objects which might cause an obstacle or oncoming traffic, and lane tracker camera unit as well as digital map data provided by e.g. a remote provider. With object data fusion, objects from environment sensors can be tracked and classified. With lane data fusion, lane data from a digital map data provider can be combined with object data fusion and a lane tracker camera for the purpose of conducting a lane data estimation.
The hierarchically ordered set describing-the predetermined-driving behavior can favorably support several functions if the driver is driving the vehicle e.g. in a lane of a road.
In the following paragraphs aspects of the invention are described when a vehicle is driving on a straight road.
According to the first preferred mode of operation elucidated above, when driving on a straight road the guiding force is selected to be positive and counteracting the current force exerted by the driver onto the steering device in situations where the operation of the steering wheel by the driver causes a current lateral velocity of the vehicle moving the vehicle laterally away from the desired lateral position. The value or amount of the guiding force can be adapted to increase (starting preferably at zero in case the vehicle is in the desired state and/or in the currently desired lateral position with zero lateral velocity) if and the more the vehicle is laterally moving away from the desired lateral position for instance at the centre of the lane.
On the other hand, for driving on a straight road the guiding force can be selected to be                (1) positive and counteracting the current force exerted by the driver onto the steering device, or        (2) negative and acting in the same direction as the current force exerted by the driver onto the steering wheel, or        (3) zero,in situations where the operation of the driver causes a current lateral velocity of the vehicle moving the vehicle laterally towards the desired lateral position. The value of the guiding force is preferably selected to be        (i) positive if the value of the current lateral velocity of the vehicle is above the value of a currently desired lateral velocity, and with its absolute amount adapted to increase the more the value of the current lateral velocity of the vehicle deviates from the value of the currently desired lateral velocity (the latter value in turn being a function of at least one of lateral distance from the desired lateral position of the vehicle, properties of the vehicle comprising additional parameters such as e.g. geometrical data (weight, height, length, width of towing vehicle and of trailer (if attached)), and curvature of the lane or road). When the vehicle is moving closer to the desired lateral position the absolute amount of the-desired lateral velocity will decrease. As an example, this means that if the vehicle has a constant lateral velocity and the vehicle is laterally moving closer towards the desired lateral position, for instance at the centre of the lane, the absolute amount of the positive guiding torque is adapted to increase,        (ii) negative if the vehicle's current lateral velocity is below the currently desired lateral velocity, and with its absolute amount adapted to decrease the more the vehicle is increasing that current lateral velocity towards the currently desired lateral velocity. When the vehicle is moving closer to the desired lateral position the absolute amount of the desired lateral velocity will decrease. As an example, this means that if the vehicle has a constant lateral velocity and the vehicle is laterally moving closer towards the desired lateral position, for instance at the centre of the lane, the absolute amount of the negative guiding torque is adapted to decrease,        (iii) zero if the vehicle's current lateral velocity is equal to the currently desired lateral velocity during the movement of the vehicle towards the desired lateral position on the road or in the lane of the road, and also at the desired lateral position and zero lateral velocity.        
The absolute value of the actual guiding force provided to the steering device will be preferably selected from an interval defined by a lower limit of preferably zero guiding force and an upper limit of a maximum guiding force.
The guiding force is added to the typical force exerted by drivers of a vehicle in such a way that the effect on the operability of the steering device is only moderate, so that even applying maximum guiding force will still guarantee the normal operability of the steering device by the driver.
Further, the guiding force—if applied and if positive, i.e. greater than zero—will always counteract any significant force exerted by the driver onto the steering device and causing a lateral velocity of the vehicle, even in situations where the driver is operating the steering device (turning the steering wheel for instance) in such a way that the vehicle is moving towards the desired lateral position on the road or in the lane of the road. The guiding force—if applied and negative, i.e. smaller than zero—will always act in the same direction as any significant force exerted by the driver onto the steering device and causing a lateral velocity of the vehicle, and will be applied only in situations where the driver is operating the steering device in such a way that the vehicle is moving towards the desired lateral position on the road or. in the lane of the road.
However, exerting too large positive guiding force values and/or applying a too large negative guiding force acting in the same direction as the force exerted by the driver onto the steering device, e.g. a steering wheel, in addition to any servo system already supporting the operation of the steering device in the usual way, would not be comfortable for the driver and could also potentially contribute to destabilize the vehicle. Therefore, when moving the vehicle away from the desired lateral position the guiding force (if applied and if greater than zero) will generally be stronger than in those situations where the guiding force is greater than zero even when moving the vehicle towards the desired lateral position, but in both cases the guiding force still has to be conform to the same boundary conditions and will always counteract the force exerted by the driver onto the steering device and causing any significant lateral velocity of the vehicle. Thus, the actual value of the exerted guiding force will decrease when the lateral velocity of the vehicle decreases and the vehicle moves towards the desired lateral position on the road or in the lane of the road within the given boundaries and increase again in case the vehicle has reached said desired lateral position and passed it moving away from it again, either by continuing the previous direction of lateral movement or by reversing said direction of lateral movement.
As an example, the force-function mentioned above could be a continuous function of a lateral distance of the vehicle, particularly of a towing vehicle, from the desired lateral position, e.g. the centre of the lane. For instance, according to the second preferred mode of operation mentioned above, the guiding force could be zero at the desired lateral position and increase with the lateral distance from the desired lateral position until the maximum guiding force is established.
According to the first preferred mode of operation elucidated above, the force-function can be a continuous function based on, for example, a fuzzy logic system using at least one of a lateral position, a lateral velocity of the vehicle, a lane curvature and possibly even a lateral acceleration of the vehicle as input variables. The value of the guiding force will be provided as the output of this system. By way of example, one appropriate fuzzy rule could be that with no lane curvature present and a high lateral velocity to the left and a lateral position in the left part of the lane, the guiding force would encourage the driver to move the vehicle towards the right side of the lane.
Another appropriate fuzzy rule when moving towards the centre of the lane (as the desired lateral position of the vehicle) with the lateral velocity in an acceptable range would result in a guiding force of zero. If the lateral velocity is deemed to be too small in this situation compared with a desired lateral velocity; the fuzzy rute˜wσαtdτesαltin a negative guiding force giving an additional support onto the steering device (e.g. a steering wheel) when, and as long as, the vehicle is moving towards the desired lateral position, for instance the centre of the lane, thereby reducing the total resistance of the steering device experienced by the driver if the steering wheel is turned in the “right” direction. If the lateral velocity is deemed to be too high in the same situation, the fuzzy rule would initiate a resisting positive guiding force when, and as long as, the vehicle is moving towards the desired lateral position, for instance the centre of the lane.
Generally, if the current lateral position of a vehicle is farther away from the desired lateral position, a larger lateral velocity of the vehicle towards the desired lateral position is acceptable than in situations where the current position of the vehicle is closer to the desired lateral position. The closer the vehicle comes to the desired lateral position, the lower its lateral velocity should be.
In the following paragraph aspects of the invention are described when a vehicle is travelling a curved trajectory along a bend of a road.
For travelling a curved trajectory along a bend the guiding force suggesting to the driver to introduce a lateral acceleration of the vehicle towards an inside of the bend can preferably be different to the guiding force suggesting to the driver to introduce a lateral acceleration of the vehicle towards an outside of the bend. Particularly, for travelling a curved trajectory along a bend the guiding force suggesting to the driver to introduce a lateral acceleration of the vehicle towards an inside of the bend can be established to be greater than for an equivalent situation on a straight road. For travelling a curved trajectory along a bend the-guiding force suggesting to the driver to introduce a lateral acceleration of the vehicle towards an outside of the bend can be established to be lower than for an equivalent situation on a straight road. By way of this the driver is encouraged-to-move-the vehicle towards to a more safe lateral position and to keep it preferably in said position. Also, the guiding force is made more comfortable and intuitive for the driver since initiating a lateral velocity towards e.g. the outside of the bend requires less force than initiating a lateral velocity towards e.g. the inside of the bend.
In the following paragraphs further aspects and advantages of the invention are described.
By providing object data fusion and lane data fusion for environment related information reliable data for lane data estimation can be obtained.
Appropriate data for vehicle related information can be at least one of wheel speed data, yaw rate data and steering wheel angle data. Wheel speed sensors can measure the velocity of each individual wheel of the vehicle. A yaw rate sensor can measure the yaw rate of the vehicle. A steering wheel angle sensor can measure the steering wheel angle of the vehicle.
When driving with a truck and an attached trailer a curved trajectory along a bend, the trailer positions itself closer to the inner side of the bend than the towing vehicle. A conventional lane keeping support system that helps to keep the towing vehicle in the centre of the lane can potentially guide the vehicle in such a way that the trailer crosses the lane border on the inside of a bend. Thus, in a preferred embodiment of the invention, wherein a trailer is attached to the towing vehicle, the desired lateral position for the towing vehicle in a bend can be estimated dependent on the desired lateral position of the trailer. Preferably, the desired lateral position of the towing vehicle can be shifted towards an outside of the bend compared to the lateral position of the trailer. Additionally or alternatively, if the trailer is predicted to leave the lane on the inside of the bend given that the towing vehicle would travel in the centre of the lane, a lane departure warning system can be disabled when the towing vehicle is leaving the lane on the outside of the bend. The driver can do this in order to make it possible for the both towing vehicle and the trailer to travel a curved trajectory along the bend and specifically preventing the trailer from departing the lane on the inside of a bend. Preferably, the warning can stay disabled during the period of time the vehicle is leaving the lane on the outside if the trailer is predicted to stay in such a situation in the lane on the inside of the bend or has to leave the lane on the inside of the bend during such a maneuver.
By steering the towing vehicle in that way on a curved trajectory along a bend, the driver intentionally steers the vehicle to leave the lane e.g. in order to prevent the trailer from entering the lane of the oncoming traffic. Other reasons for doing so can be to prevent the trailer from leaving the lane at a road border or e.g. to prevent the trailer from leaving the lane into an adjacent lane with traffic going in the same direction. Oncoming traffic is to be understood as traffic which is driving in opposite direction of the vehicle, e.g. on a two-way road. This is particularly advantageous if the curvature is large, i.e. a small bend radius and/or a small lane width.
In a preferred embodiment, a predictive “look-ahead” function can be implemented, since the lateral position of the trailer cannot be adjusted-at once. Thus, an early corrective movement of the towing vehicle is possible which can prevent the trailer from leaving the road on the inside of a bend ahead. Centre of the road or centre of the lane means the lateral centre of the road or the lane with regard to the regular driving direction of the vehicle.
According to a further preferred embodiment, a guiding force can be adjusted depending on a classification of the road. Favorably, in case the probability that an adjacent lane exists exceeds a predefined threshold and the system decides to provide a guiding force to prevent a lane departure in that direction, the guiding force can be chosen to be lower than in case no adjacent lane is present. For example, a predefined probability threshold for the probability that an adjacent lane exists can be set to 50%. If a probability that an adjacent lane exists is detected which is more than 50%, the guiding force which may be provided to the steering wheel can be lowered when the vehicle risks to leave the lane to the side of the adjacent lane mentioned above.
Preferably, at a road border with no adjacent lane the guiding force can be higher when the vehicle is moving towards said road border.
Most lane departure warning systems known in the art trigger a warning when the vehicle crosses the lane border or when the predicted time to a lane departure is lower than a fixed threshold. An advantageous embodiment of the invention is to trigger (enable) the lane departure warning when the predicted time to a lane departure is less than a variable threshold. Preferably, the variable threshold is a function of the magnitude of the current lateral velocity of the vehicle. Preferably, the threshold will be smaller for low magnitudes of lateral velocity than for high magnitudes. According to the preferred modes of operation of the invention-described above, the guiding force can be triggered-in-such a-situation where the predicted time to a lane departure is lower than said (variable) threshold. Alternatively, the guiding force can be continuously applied within its limits.
A high threshold at high lateral velocities of the vehicle advantageously gives the driver an earlier warning and therefore more time to react in order to avoid a potential lane departure. This is more important at high lateral velocities than at low lateral velocities since it takes more time to bring the vehicle to a steady-state with regards to lateral velocity.
In case the driver should prefer to drive close to a lane border at zero or low lateral velocity, if the warning is triggered on a high threshold, small errors (e.g. signal noise) on input data result in false alarms, i.e. the warning is activated although the vehicle probably will not cross the lane border in such a situation. To avoid this, the preferred solution elucidated above proposes a low threshold for low or zero lateral velocities in order to minimize in these situations the risk of false alarms. If for instance the threshold is set to zero at low lateral velocities the warning will preferably be triggered when the vehicle actually crosses the lane border. While this is acceptable in case of low lateral velocities of the vehicle, this would not be desirable in case of high lateral velocities since in that situation a low or zero threshold would give the driver considerable less time to react to a potentially critical situation.
In case of a lane departure of the vehicle in lateral direction towards the road centre while travelling a curved trajectory along the bend, a guiding force can be determined according to traffic conditions.
According to a preferred embodiment of the invention, the guiding force is provided depending on expected oncoming traffic. In case oncoming traffic is detected and provided that the system is activated, the guiding force decided to be supplied will be increased in its absolute amount, i.e. for negative and positive values of the guiding force, whatever is applied. Accordingly, the guiding force will guide stronger towards the desired lateral position, i.e. the centre of the lane, thereby reducing the risk of curve-cutting and increasing the vehicle safety.
In a similar way, the guiding force is provided depending on expected overtaking traffic. In case overtaking traffic is detected and provided that the system is activated, the guiding force decided to be supplied will be increased in its absolute amount, thus guiding stronger towards the desired lateral position, i.e. the centre of the lane.
If an intentional lane departure is planned, the guiding force can be deactivated. If the system or guiding force is deactivated, preferably a warning signal can be issued in order to keep the driver alert. Deactivating the system or the guiding force is to be understood in the way that temporarily the lane keeping support system does not provide any guiding force. Basic functions of the system, however, are preferably still enabled, such as sensors surveying oncoming traffic etc. Particularly, when a critical situation is detected, in a preferred embodiment of the system, a guiding force and/or another warning signal can still be provided and/or—as an option—for instance an emergency-braking-maneuver can be initiated, depending on the circumstances.
The system can enter the deactivated state automatically if it is detected that a lane departure is intentional, e.g. if a direction indicator is activated when leaving the lane for overtaking another vehicle. Optionally an intentional departure from a desired lateral position can also be estimated by analysis of the sensor data provided for vehicle and environment related information.
The warning signal can either be a signal warning the driver that the vehicle is going to leave the centre of the lane or a signal warning the driver that the lane keeping support system is currently not providing a guiding force or both. The warning signal can be for instance an optical and/or a haptic and/or an acoustic signal. Preferably, the optical signal is also visible for the driver and the acoustical signal is also audible for the driver, as well as the haptic signal being also tangible for the driver. For instance, the haptic signal could be a tangible vibration of the steering wheel or of the driver's chair (or part of it).
According to another aspect of the invention, a lane keeping support system for a vehicle for performing the method is proposed, having a support unit which comprises a data fusion module for generating environment related information based on at least partly fused data, a trajectory predictor module for predicting a future trajectory of the vehicle, an estimator module for estimating a desired lateral lane position of the vehicle and/or a guiding force and a decision system module for deciding if a guiding force should be provided and, if to be provided, for defining an amount of such guiding force depending on a hierarchically ordered set describing a predetermined driving behavior of the vehicle, adapting said amount of guiding force depending on the direction in which the vehicle is intended to move and activating one or more actuators for supplying said adapted amount of guiding force to the steering device, with one or more inputs for sensor data for the data fusion module, one or more inputs for vehicle related data and one or more outputs for an output of guiding force demand and/or warning signal.
Optionally, an adjacent space classifier can provide input data to the force estimator. The classifier can be a system including sensors which classify the adjacent space to the current lane of the vehicle. The system can determine whether or not the space next to the current lane is adapted for continuing the intended driving, e.g. whether there is another lane next to the current lane serving as an accessible area for the intended operation of the vehicle or e.g. a ditch not permitting such operation. Appropriate sensors can provide information about objects in the adjacent area and/or surface information in the adjacent area. This information can be utilized to estimate the probability that an adjacent lane exists.
The lane keeping support system does not replace the driver or override the driver's will wherein the driver still has full authority over the operation of the vehicle. Particularly, the lane keeping support system can be switched off if the driver does not want an action from the lane keeping support system. When the system is deactivated, reasonably a haptic optical, and/or acoustical warning signal indicates that the system does not provide any guiding force. However, although no guiding force is provided in this state, basic functions can still be active in the background and a guiding force can preferably still be provided if in this state a critical condition is detected.
Furthermore, the level of the guiding force can always be adapted to make it possible for the driver to override the system by turning the steering wheel to an arbitrary position. When the system is active, it is preferably checked with appropriate sensors if the driver has his hands on the steering wheel, for instance using a camera, a capacity sensor coupled to the steering wheel, or the like. This helps to avoid an abuse of the lane keeping support system as an “autopilot”.
Another aspect of the invention provides a computer program comprising a software code adapted to perform a method or for use in a method exhibiting at least one of the features elucidated above when said program is run on a programmable microcomputer; adapted to be downloaded to a support unit or one of its components when run on a computer which is connected to the interne.
Further, a computer program product stored on a computer readable medium is proposed, comprising a software code for use in a method exhibiting at least one of the features elucidated above on a computer.
Another aspect of the invention provides a computer program product stored on a computer readable medium, comprising a program code for use in a method for supporting lane keeping of a vehicle equipped with a steering device operated by a driver, the method comprising at least the steps of                combining vehicle and environment related information;        predicting a future trajectory of the vehicle based on vehicle and environment related information;        estimating a desired lateral lane position and/or a guiding force;        comparing the future trajectory and the desired lane position;        deciding if a guiding force is to be provided to the steering device;        if guiding force is to be provided                    a) defining an amount of said guiding force depending on a hierarchically ordered set describing a predetermined driving behavior of the vehicle;            b) adapting said amount of guiding force depending on the direction in which the vehicle is intended to move.                        
Such Computer program product may even comprise a program code for use in such method, where the method also comprises the step of                c) activating one or more actuators for supplying said adapted amount of guiding force to the steering device.        
In the drawings, identical or similar elements are referred to by equal reference numerals. The drawings are merely schematic representations, not intended to portray specific parameters of the invention. Moreover, the drawings are intended to depict only typical embodiments of the invention and therefore should not be considered as limiting the scope of the invention.